This invention relates to various kinds of novel optical functional elements and optical transmission and receiving devices based on waveguide means having holograms which generate radiation modes.
More specifically, the invention relates to a distributed feedback (DFB) laser emitting radiation-mode light normal to the substrate surface and its manufacturing method.
The invention also relates to a waveguide type optical isolator, distributed feedback laser being compact, high in directional selectivity and good in optical coupling, and a monolithically integrated optical element containing them.
The invention further relates to optical functional elements such as optical amplifier, optical modulator, laser oscillator, and so forth, having a resonator means, for high-efficiency amplification of radiation modes emitted from the waveguide means, and optical transmission and receiving devices using them.
Optical functional elements having a waveguide for guiding light waves involve semiconductor lasers. Conventional semiconductor lasers utilize a single waveguide structure as a resonator. A semiconductor optical amplifier (SOA) similarly has a single waveguide structure. A grating-coupled surface-emitting laser (GCSEL) also utilizes a single waveguide structure sometimes with a single vertical reflector placed on the substrate side for recycling the radiation mode emitted towards substrate by changing its direction toward surface. That is, any of conventional optical functional elements was based on the concept of one resonator means utilizing one-way feedback.
Since this conventional concept is a common knowledge, here is omitted detail explanation on structures of conventional optical functional element with reference to drawings. A drawback of these conventional techniques lies in the lack of extensibility and flexibility because of using only one resonator means.